The invention relates to a water-based system for altering wettability of porous media and, more particularly, to a method for using such a system to improve hydrocarbon production from subterranean porous formations.
In the production of hydrocarbons from subterranean hydrocarbon bearing formations, formation wettability is an important parameter which affects fluid flow through the reservoir. Wettability is a manifestation of rock-fluid interactions, and hydrocarbon reservoir rocks exhibit different wetting conditions. Reservoir rocks can be considered as strongly and weakly water wet, strongly and weakly oil wet, and intermediate wet. These wetting conditions are dictated by the mineral or rock surface, fluid composition, physical-chemical properties, temperature, pressure and the like.
Since wettability is an important parameter in the recovery of hydrocarbons, it is desirable to be able to alter or adjust wettability to gain additional control over the production process.
Unfortunately, conditions in subterranean formations tend to be harsh, and modification of reservoir wettability is therefore difficult.
Further, other reservoir properties such as permeability and porosity are critical to good hydrocarbon production and must be protected.
It is the primary object of the present invention to provide a method and system whereby wettability of a reservoir formation can be altered as desired.
It is a further object of the present invention to provide a method and system which are resistant to harsh reservoir conditions.
It is a still further object of the present invention to provide such a method and system which can be applied to enhance production from existing hydrocarbon-producing wells while avoiding any substantial impact upon formation porosity or permeability.
Other objects and advantages of the present invention will appear hereinbelow.
In accordance with the present invention, the foregoing objects and advantages have been readily attained.
According to the invention, a method is provided for altering wettability of a reservoir formation, which method comprises the steps of providing a water-based fluid containing a wettability altering coating system; and flowing said fluid into a reservoir so as to coat said reservoir with said coating system.
In accordance with a preferred aspect of the present invention, the fluid comprises an aqueous solution system comprising a combination of organic and inorganic components having nanoparticle size.
The organic nanoparticles are preferably polymeric structures which are adsorbed on the mineral surface leading to the formation of a film on the mineral surface so as to alter wettability as desired without substantially affecting formation permeability or porosity.
The inorganic nanoparticles are selected to help control viscosity of the fluid as desired.
In further accordance with the invention, the flowing step can preferably be accomplished by flowing the fluid into the reservoir with the fluid under pressure, and holding the pressure until the coating system has cured.
In accordance with a further aspect of the present invention, it has been found that an intermediate wetting condition is most desirable for enhancing hydrocarbon production from a reservoir. Thus, according to the invention, the method is ideally utilized with reservoirs having a wetting condition selected from the group consisting of strongly water wet and weakly oil wet, or strongly oil wet and weakly water wet, and the coating system is preferably selected so as to provide the reservoir with a desired wetting condition which may be an intermediate or some other wetting condition.